Process of reducing and separating silver.



PATENTED JUNE 2, 1903.. G. v. GUZMAN. PROCESS OF REDUCING AND SEPARATINGSILVER.

APPLICATION FILED KAY 19, 1902.

N0 MODEL.

fizz/612601": Gem/d9 I aca Guzman,

-www UNITED STATES Patented June 2, 1903.

PATENT OFFICE.

(GERARDO vAoA GUZMAN, or SUCRE, BOLIVIA.

SPECIFICATION forming part of Letters Patent N 0. 729,760, dated June 2,1903. l Application filed May 19, 1902. Serial No. 107,891. (Nospecimens.)

.To all whom it may concern:

Be it known that I, GERARDO VACA GUZ- MAN, a citizen of Bolivia,residing in Sucre,

Bolivia, have invented certain new and useful Improvements in Processesof Reducing and Separating Silver, of which the following is aspecification. V

The present invention relates to theextraction and reduction'of metallicsilver from ores so poor as to render any process of smelting or fusioninapplicable.

It more particularly refers to the extraction of metallic silver fromargentiferous blendes and galenas which when the proportion of silverwas below a certain amount was not 0011-.

sidered worth extracting.

' It is old in the art of extracting silver froml argentiferous ores toadd an impure mixture of cupric and ferric salts called magistral to awatery mass of ore, common salt, and

. mercury, this process being known as the Patio process, from whichmixture finally the mercury was distilled and the silver left behind.The chemical reaction during this process is as follows: The sulfates ofcopper and iron in the magistral are converted by the sodium chloridintofthecorresponding chlo-.

rids, which then react with the silver sulfid to'form silver chlorid.The thus-resulting silver chlorid is held in solution by the sodiumchlorid and on adding metallic mercury is decomposed, yielding calomeland metallic sil-.

'ver. All the mercury converted into calomel is lostfor the pr0cess,andthis makes the proc ess itself, therefore, quite expensive. It is alsoknown that cuprous chlorid in the presence of sodium chlorid changes thesilver sulfid into the silver chlorid, formin thereby metallic copper,

rated dissolves the silver chlorid. This solubility has been made use ofin the Angustine process, inwhich'the silver is precipitated from thedouble chlorids of .silver and sodium by means of metallic copper; butthis process has not yielded satisfactory re sults and was in timesuperseded by the Ziervogel process,consisting in the separation of thesilver from the sulfid by lixiviationwith arseniureted combinations ofsilver by lixiviating the same with sodium thiosulfate in order todissolve the silver chlorid and afterward saving an additional amount ofsilver by adding copper thiosulfate. ical reaction taking place in theextraction of silver from chloridized ores was not understood for quitesome time, and it was believed that as cuprous chlorid was produced asone of the by-products of the reaction of cupric chlorid with silversulfate both cupric and cuprous chlorids were present in the reagent atthe same time. This error has been correctedlong ago,and itwasconclusively shown that such reaction cannot take place. All theseprocesses require the use of comparatively richer ores andaresubstantially not applicable in the treatment of blendes and galenas.

The main object ofthe present invention,

therefore, is to supplya process for the treat ment ofpoor ores and ofargentiferous blendes and galenas which heretofore were not fit for anyofthe known metallurgical processes.

Another object of the present invention is to supply. a process which incertain cases does not require roasting or chloridization of the ores.

A further object is to furnish a process which facilitates the processof and time in extracting silver and which is less expensive than any ofthe processes known heretofore and gives better results thanlixiviatiomamal gamation, to. l l

For these purposes thepresent invention consists in the employment of acertainsolution which has a chloridizing and at the same time adissolving effect and which acts upon the roasted and chloridized oreseven when the chloridiziiig was entirely incomplete. It

The chemchanges the silver suliid which has not been decomposed duringthe roasting process, as Well as the antimoniates and arsenates ofsilver formed during the roasting process into the silver chlorid. Thissilver chlorid just formed, together with that formed in the previousroasting and chloridizing process, is dissolved in the said solution,from which it is precipitated or reduced to metallic silver by means ofmetallic copper or lead. This principal solution or reagent employedconsists of a mixture of cupric chlorid and cuprous chlorid, in whichthe former always predominates. As stated hereinbefore, cuprous chloridhas been used heretofore for transforming silver sulfid into the silverchlorid; but its stability in solution is so small that shortly afterits formation it loses to a great extent its chloridizing propertiesupon the sulfureted, antimoniureted, and arseniu'reted silver by beingreduced to cuprous oxychlorid. A solution of cupric chlorid is moresteady and has similar chloridizing properties upon silver compoundsexisting in argentiferous ores, and a mixture of the two gives the mostsatisfactory results, and the reactions taking place in the process ofextracting silver are as follows:

Ag S+ (11101 2AgCl+ (JuS.

Ag S Ou Cl =2AgOl+ CuS Cu.

This double solution of cupric chlorid and cuprous chlorid is preparedby pulverizing and sieving copper pyrites and mixing the same withtwenty per cent, in weight, of so dium chlorid. This mixture is thenroasted for about two hours at not more than darkred heat, whereby athorough calcining and chloridizing takes place. The roasted mixture isnow placed into a vat, and a sodiumchlorid solution of about 20 to 25Baum, having a temperature of about 100 centigrade, is passed throughthe same and tapped off from the vat, containing now the cupric chloridand cu prous chlorid in solution in the proper proportion for use in theprocess of extracting silver.

The accompanying drawings, forming part of the present application,illustrate in Figure 1. a perspective view of a plant for extractingsilver from its ores according to the present invention. Fig. 2illustrates a device for washing the metallic silver, and Fig. 3 shows asimple device for removing the silver adhering to the granulated copper.

The ehloridizing and dissolving reagent, prepared as statedhereinbefore, is placed in a vat 1, constructed of wood or masonry. Byopening the drain-cocks 2 it runs into a filtering-box 3,providedwith aseries of cone-shaped bag-filters 4, and through those into acollecting-tank 5. From there the solutionis drained off through cocks Ginto a tank '7, in which it may be heated from a boiler 8 by means ofsteam-coils 9. The roasted and pulverized ore is placed on removablescreens 12 of a lixiviating-vat 11. The reagent is delivered from thecollecting-tank 5 into the lixiviating vat 11 through a drain-cock 10and acts now upon the ore according to the formulas hereinabove setforth. The liquid discharged from this tank 11 through the cock 13,located near the bottom of the tank 11, contains the silver chlorid andpasses first into a receiving and distributing tank 14 and from there,by means of a pipe or pipes 15, into a series of slightly-cone-shapedvats 16. The drawings illustrate only one set of vats; but more sets maybe arranged parallel to each other by employing more discharge pipes 15.

The vats 16 are provided with removable filters 18 and communicate amongthemselves by means of rubber tubes 17. The vats 1b are located ondifferent levels and the liquid passes from the higher to the lower bymeans of the rubber tubes 17, so that the liquid already filtered in oneof the vats is passed to and filtered again in the other vats. Thefilters 18 are covered with the reducing agent, consisting of granulatedmetallic copper or lead. In these vats 16 the silver is now reduced toits metallic state and deposited upon the granulated reducing agentplaced on the filters 18. If copper is employed as a reducing agent, thereduced silver is very pure and consists of comparatively largecrystals,which have no tendency of clogging the filters 18. When lead isemployed as a reducing agent, the liquid must enter the vats 16 frombelow, thereby rising upward through the filters 18; otherwise thefilters 18 would become clogged very soon by the silver precipitate,which in this case consists of relatively fine powder mixed with leadand zinc salts.

The liquid which has passed through the vats 16 is nearly entirely freefrom silver, but contains lead, zinc, and copper salts, especially when.blendes and galenas have been treated, and it becomes necessary toeliminate these salts before reusing the solution. For this purpose aprecipitation-tank 191s provided, having overflow-pipes 20 connected tococks 21. The pipes 20 are preferably made of rubber and fastened belowa float, (not shown in the drawings,) so as to decant always theuppermost strata of the contents of the tank 19. This tank containslime-water saturated with common salt, and the lead, zinc, and coppersalts are precipitated therein in the form of hydroxids and may beremoved from the bottom thereof from time to time. The cocks 21discharge the liquid through a filtering-box 22, provided with a seriesof bag filters 23, into a collecting-tank 24 and from there throughfacock 25 into a receiving-tank 26. From here the regenerated solution maybe withdrawn througha pipe 27 and by means of a pump 28 forced backthrough pipe 29 into the upper tank 1 in order to be used over again inthe process of extraction. When the ores treated by the solution do notconsist of blendes or galenas and if copper has been employed as areducing agent, the regenerated solution contains substantially theoriginal proportion of cupric chlorid and enprous chlorid. If the lattershould be in excess, it may easily be eliminated in part by agent in thevats 16 the contents of the iil ters 18 are discharged, the productdried, and the silver separated from the coarse granulated reducingagent by sieving. The silver is placed into the washing apparatusillustrated in Fig. 2, which consists of a vat 30, provided in its lowercone-shaped part 31 with canvas filters, which allow the water to passthrough but retain the metallic silver. Through a pipe 32, reaching tothe bottom of the vat 30, hot water is charged into thevat'30, whichdissolves all the remaining salts that could have adhered to the silverand then is drained off through a tap 33 into a tank 0i, through thefiller 35 into a receiver 36, in which receptacles any trace ofsilvermay be collected which accidentally may have remained in the water.

The granulated metal used as a reducing agent, which may have somesilver adhering thereto, can be placed into a barrel 37, Fig. 3,rotatably mounted on a shaft 38 and operated by means of a pulley 39.The metal is mixed with water and agitated until the silver and theoxids have been mechanically removed from the granulated metal, and thenthe contents of the barrel are discharged through the tap-hole 40 intothe collectors 41, then the tank t2, and through the filters l3 into thereceiver 44.- The reducing agent is retained in 4:1 and the metallicsilver in the filters 43. The silver collected in the filters 18, 85,and 43 is almost pure and can be melted and refined in the usual manner.

The ores used in this plant are preferably roasted in open-air furnacesand crushed and pulverized so that they pass a No. 40 to wire process.do not require roasting or calcining, the soluscreen. In the treatmentof argentiferous blendes or galenas ten per cent. of iron pyrites ispreferably added before the roasting lVhen ores are to be treated whichtion in tank 7 is preferablyheated, and if much copper pyrites should becontained in the ores it will not be necessary to add cuprous chlorid t0the regenerated solution, for the same is formed in suiiicientquantityin the lixiviation= tank 11. Crude ores after chloridizing androasting may preferably be washed on the filters 1.2 in the vat 11 bymeans of hot or cold water.

Having now described the present invention, that which is considered newand useful,- and is desired to be secured by Letters Patent, is-

1; The process of extracting and separating silver from its ores, whichconsists in subject' ing the ores to the action of a preprovidedsolution containing predetermined quantities of more than one of thechlorids of copper; passing the resulting solution through a reducingagent, and removing and collecting the metallic silver from saidreducing agent.

2. The process of extracting and separating silver from its ores, whichconsists in subjecting roasted ores to the action of a prepro-' videdaqueous solution of cupric' chlorid and cuprous chlorid, passing theresulting solu tion through granulated metal, and removing andcollecting the metallic silver from said metal.

The process of ext acting and separat ing silver from its ores, whichconsists in subjecting roasted ores to the action of a preprovidedaqueous solution containing predetermined quantities of cupric chloridand cuprous chlorid, passing the resulting solu tion through granulatedcopper, and removing and collecting the metallic silver from saidcopper.

GERARDO" VAOA GUZMAN.

Vitnesses:

RALPH JULIAN LACHERS, FRED. J. DOLE.

